Two-component polyurethane polyurea casting systems (hereafter abbreviated to "PUR-casting systems") which react at room temperature or slightly elevated temperature and which have a potlife (casting time) which can be adjusted to a desired length, and, which, nevertheless, exhibit rapid final hardening (fast to handling and non-crushable, dry on the surface) after the onset of hardening, are so far not known. The long potlife systems with "cold setting" described so far all suffer from the disadvantage that either the casting time is no longer than 20 to 30 minutes or the final hardening extends over days.
The object of the present invention was thus to find a 2-component PUR-casting system which comes as near as possible to the ideal cold setting 2-component PUR-casting system: i.e., has a potlife which is long or adjustable as desired at room temperature, and a setting time not much longer than the potlife.
The production of suspensions which are stable under storage at room temperature but are heat-hardenable, from a solid finely-divided polyisocyanate, which is deactivated by partial chemical reaction on the surface, preferably with aliphatic polyamines and is suspended in at least one compound which is reactive with isocyanate groups, for example high molecular weight polyols and/or polyamines, is known. See, e.g., U.S. Pat. Nos. 4,483,974; 4,400,497; 4,546,165; and 4,581,432; and U.S. application Ser. Nos. 732,028 (filed on May 8, 1985) and 732,039 (filed on May 8, 1985). Such deactivated polyisocyanates are prepared by reacting solid polyisocyanates with, for example, polyamines, hydrazines, hydrazide compounds, amidine compounds, or guanidine compounds. Solid polyisocyanates are produced which are stabilized by means of sheathing with polyaddition products, and which have a retarded reactivity. The sheathing is substantially formed from polyaddition products in a thin layer and in only a subequivalent reaction of the NCO groups (from 0.1 to 25%) on the surface of the solid isocyanate particles with the deactivators. By stabilizing with polyadduct sheathing, polyisocyanate particles are obtained which in one-component reactive system, (i.e., as a suspension in the presence of high molecular weight polyols and/or high molecular weight polyamines) only react as polyisocyanates above a certain temperature. Below this temperature, however, they are stable under storage.
In the known one-component PUR-casting compositions, the isocyanates and isocyanate-reactive components are contained in the already correct ratio for the production of the finished PUR-plastics materials. The hardened polyurethanes are produced by simple heating of the one-component casting mixtures which are storable for the desired duration, to temperatures of from 70.degree. to 180.degree. C., preferably from 100.degree. to 130.degree. C. The mixtures are stable under storage at room temperature or slightly elevated temperature, i.e., they enter into no detectable reaction. There are no indications in the above-noted literature of a cold-setting, one-component PUR-casting composition, apart from cold setting by insufficient stabilization in the production of the one-component mixtures, which, however, is not regarded as true one-component PUR-casting mixtures. Such insufficiently stabilized one-component casting mixtures can likewise not be characterized as cold-setting two-component PUR-casting mixtures since they could only be produced at the place of application immediately before use. Furthermore, the homogenous mixing of solid, finely-powdered isocyanates with polyol/polyamine components requires particular mixing assemblies which are not always available on the spot, especially in the open air. The problem with the two-component polyurethane mixing technique thus cannot be solved by the use of insufficiently stabilized one-component systems of the above described type.